Hexanoylglycine as biomarker for the predisposition for weight gain and obesity

ABSTRACT

The present invention relates generally to the field of nutrition and health. In particular, the present invention relates to a new biomarker, its use and a method that allows it to diagnose the likelihood to resist diet induced weight gain, and/or to be susceptible to a diet induced weight gain. For example, the biomarker may be hexanoylglycine.

The present invention relates generally to the field of nutrition andhealth. In particular, the present invention relates to a new biomarker,its use and a method that allows it to diagnose the likelihood to resistdiet induced weight gain, and/or to be susceptible to a diet inducedweight gain. For example, the biomarker may be hexanoylglycine. Thisbiomarker may also be used for diagnosing/monitoring the effect of achange in lifestyle on weight gain risk in a subject.

Obesity has become one of the most important global healthcare problemsin the 21st century as it raises the risk to develop further diseasesincluding type 2 diabetes, hepatic steatosis (NAFLD), cancers, arthritisand cardiovascular diseases (CVD). The aetiology of obesity results froma complex interaction between genetic and environmental factors such ashigh caloric diet, lack of physical activity and behaviour. Gutmicrobiota being involved in various physiological functions such as thematuration of gut's innate immune system and the digestion/absorption ofnutrients also influences the development of several metabolic diseasesand seem to have a significant impact on obesity. Hence, individualpredisposition of developing obesity varies according to thesemulti-factorials causes.

Ingestion of an unbalanced diet rich in fat and/or carbohydrate has beenassociated with an increased rate of triglyceride storage in adiposetissues as well as lean tissues such as liver, muscle and heart. Thisectopic fat deposition inducing lipotoxicity is also correlated with arange of metabolic disorders such as hypertriglyceridemia, hypertension,high fasting glucose and insulin resistance (IR). Nonetheless, someoverweight or obese people may develop various metabolic disorders andwhile others stay healthy. For instance, the localisation of fatdeposition in the body influences the development of metabolicdisorders. Epicardial fat, being efficient to release proatherogenicadiponectines and process fatty acids, has been positively correlatedwith CVD markers in humans. By contrast, intra-hepatic fat has beenassociated with inflammation and insulin resistance. Wildman et al. alsohighlighted that race-ethnic differences in healthy middle age women areassociated with differential metabolic activity of visceral andsubcutaneous adipose tissues which could influence the ethnic-relatedpredisposition to develop obesity and CVD As a result, it is relevant toidentify the likelihood to develop obesity-related metabolic disordersat an early stage, in order to assess the individual metabolic statusand to effectively prevent the development of metabolic diseases.

It would therefore be desirable to provide the art with a method thatallows it to identify subjects early—ideally before they put onweight—that are likely gain weight when consuming diets rich in fats.

Any reference to prior art documents in this specification is not to beconsidered an admission that such prior art is widely known or formspart of the common general knowledge in the field.

The object of the present invention is to improve the state of the artand in particular to provide a method that allows it to effectivelystratify people early whether or not they are likely to respond to ahigh fat diet with weight gain.

The inventors were surprised to see that the object of the presentinvention could be achieved by the subject matter of the independentclaims. The dependent claims further develop the idea of the presentinvention.

Accordingly, the present invention provides a biomarker, its use and amethod for diagnosing the likelihood to resist a high fat diet inducedweight gain.

As used in this specification, the words “comprises”, “comprising”, andsimilar words, are not to be interpreted in an exclusive or exhaustivesense. In other words, they are intended to mean “including, but notlimited to”.

The inventors have used a metabonomics approach to achieve the objectiveof the present invention. Metabonomics is considered today awell-established system approach to characterize the metabolicphenotype, which comprises the influence of various factors such asenvironment, drugs, diet, lifestyle, genetics, and microbiome factors.Unlike gene expression and proteomic data that indicate the potentialfor physiological changes, metabolites and their dynamic concentrationchanges within cells, tissues and organs, represent the real end-pointsof physiological regulatory processes.

It is therefore a suitable approach to investigate the gradual metabolicchanges linked to various dietary interventions and diseasesdevelopment. Recently, metabolomics and lipidomics-based discoverieshave been accelerating our understanding of disease processes, and willprovide novel avenues for prevention and nutritional management of thesub-clinical disorders associated to metabolic syndrome. In particular,“omics” data have highlighted the contribution of energy metabolism(Krebs's cycle), lipid and amino acid processing, as well asinflammatory signals to the onset of obesity and IR.

Using a combination of proton nuclear magnetic resonance (¹H NMR)spectroscopy of urine samples collected overtime and weight gainmonitoring, the inventors have identified novel metabolic biomarkers ofgradual weight gain induced by high fat diet in a well defined C57BL/6Jmouse model. This animal model is well known to show extreme phenotypesacross isogenic animals, i.e. animals resistant or prone to high fatinduced weight gain distribution. The present inventors havecharacterised the short term (7 day) and long term (60 day) metabolicadaptation of C57BL/6 mice fed with a high fat diet (HFD) and haveestablished the specific metabolic signatures associated with phenotypevariability within HFD fed mice, i.e. animals resistant or prone to highfat induced weight gain. By using a metabonomic approach, the inventorshave showed that mitochondrial metabolic pathways (fatty acid βoxidation, branched-chain amino acid catabolism, butanoate metabolism,nicotinamide adenine dinucleotide pathway and Krebs's cycle) are quicklyup-regulated by high fat feeding which might reflect a fatty acidsaturation of mitochondria and an impairment of energy metabolism.

The inventors could show that obesity resistant mice under HFD areassociated with a specific activation of mitochondrial oxidativepathways (β oxidation, butanoate metabolism and leucine catabolism)which may be a protective mechanism against fatty acid overloading.

These results emphasize the role of mitochondria in obesity developmentand allows the conclusion that the likelihood to develop metabolicdisorders, such as obesity, can be determined from an early metabolicsignature using a specific set of biomarkers that the inventors haveidentified.

The inventors were able to show that the urine metabolic response afterone week on high fat feeding (Day 7) enables not only the prediction ofthe final weight gain for each individual (Day 60), but also to stratifyanimals according to their predisposition to be resistant or prone tohigh fat induced weight gain.

Consequently, the present invention relates to a novel biomarker,hexanoylglycine.

The invention further relates to the use of hexanoylglycine as abiomarker in urine for detecting and/or quantifying the likelihood toresist high fat diet induced weight gain.

Similarly, the invention also relates to the use of hexanoylglycine as abiomarker in urine for detecting and/or quantifying the likelihood to besusceptible to high fat diet induced weight gain.

The invention also relates to a method of diagnosing the likelihood toresist high fat diet induced weight gain in a subject, comprisingdetermining the level of hexanoylglycine in a urine sample previouslyobtained from a subject to be tested, and comparing the subject'shexanoylglycine level to a predetermined reference value, wherein thepredetermined reference value is based on an average hexanoylglycinelevel in urine in a control population, and wherein an increasedhexanoylglycine level in the sample compared to the predeterminedreference value indicates an increased likelihood to resist high fatdiet induced weight gain. Similarly, the invention also relates to amethod of diagnosing the likelihood be susceptible to high fat dietinduced weight gain in a subject, comprising determining the level ofhexanoylglycine in a urine sample previously obtained from a subject tobe tested, and comparing the subject's hexanoylglycine level to apredetermined reference value, wherein the predetermined reference valueis based on an average hexanoylglycine level in urine in a controlpopulation, and wherein a decreased hexanoylglycine level or the absenceof change in the sample compared to the predetermined reference valueindicates a increased likelihood to be susceptible to high fat dietinduced weight gain.

This biomarker of the present invention may also be used for diagnosingand/or monitoring the effect of a change in lifestyle on weight gainrisk in a subject. For this the biomarker level may be assessed beforethe lifestyle change and the resulting level may be compared to thelevel of the said biomarker after the lifestyle change.

FIG. 1: Variability of body weight gain in a population of n=56 mice feda HFD. (A) Experimental design. (B) Body weight distribution of miceafter 7 days and 60 days of HFD feeding. (C) Identification ofnon-responder (NR) and strong responder (SR) mice to obesity at eachtime-point. Several NR and SR mice are observed in 2 time points orduring the overall course of the experiment. (D) Weight monitoring ofcontrol (n=24), NR (n=30), and SR (n=29) mice before the diet (t0),after 7 days (t1) and 60 days (t2), of HFD feeding. s(n=average±standarderror, p value for non parametric Mann and Whitney test *<0.05,**<0.001, ***<0.0001.)

FIG. 2: ¹H NMR urine metabolic profile of C57BL/6 HFD fed or LFD fedmice 7 days and 60 days after the diet switch. (A) Mean ¹H NMR spectrumof urine from LFD fed mice or (B) HFD fed mice. (C) OPLS-DA score plotof urine metabolic profile of LFD and HFD fed mice at 7 days (D) OPLS-DAscore plot of urine metabolic profile of LFD and HFD fed mice at 60days. (E) Heatmap obtained from the OPLS-DA coefficient plots showedmetabolites found to be significantly different in HFD and LFD fed mice.Correlation values of the metabolites are displayed by color code.(Gradient of red color for metabolites positively correlated withHFD-fed mice and gradient of blue colors for metabolites negativelycorrelated).

FIG. 3: Specific metabolic signature of NR and SR mice. (A) Mean of ¹HNMR spectra of urine from NR mice or (B) SR mice. (C) OPLS-DA score plotof urine metabolic profile of NR and SR mice at 7 days (D) and 60 days.(E) Heatmap obtained from the OPLS-DA coefficient plots showedmetabolites found to be significantly different in NR and SR mice.Correlation values of the metabolites are displayed by color code.(Gradient of red color for metabolites positively correlated with SRmice and gradient of blue colors for metabolites negatively correlated).

FIG. 4: Mapping of the urinary excretion pattern of metabolites involvedin BCAAs, butanoate, Nicotinamide adenine dinucleotide metabolism,Krebs's cycle and β oxidation. The bar plots showed the mean ratio withstandard error of metabolite integrals at day 7 to day 0 or day 60 today 0. The Y axis indicates the value of the mean for LF, HF, NR and SRmice (arbitrary unit). Significant difference between mean ratios of LFand HF or NR and SR were calculated with non parametric Mann Whitneytest: *<0.05, **<0.001, ***<0.0001. Indirect metabolic reactions arehighlighted with dash arrows.

FIG. 5 shows metabolite importance and robustness in predicting NR andSR as assessed by Random forest analysis.

Table 1: Summary of relationships between metabolites and weight gain inhigh fat induced weight gain

Table 2: Summary of the fold of changes in selected metabolites overtime in weight gain resistant (NR) and prone (SR) individuals

The present invention relates in part to a biomarker, wherein thebiomarker is hexanoylglycine.

In the experiments described herein, mice fed with an HFD displayed aurinary increase of hexanoylglycine over time. Without wishing to bebound by theory, the inventors currently believe that hexanoylglycine isobtained in vivo from the conjugation of hexanoyl-CoA with glycine inthe liver and is then excreted in urine. Hexanoyl-CoA is an intermediatemetabolite of β-oxidation and carnitine is responsible for the uptake offatty acids in mitochondria which is a key initial step in the βoxidation process. These results hence suggest an up-regulation of fattyacid break down through β oxidation and emphasize the saturation ofoxidative fuel in the mitochondria which might alter energy homeostasis.The increase of several Krebs's cycle intermediates and end-products ofnicotinamide adenine dinucleotide pathways in urine of HFD mice may beconsidered evidence for energy over-production. The chronic increase ofmitochondria oxidative pathways are considered to be deleterious for themitochondria leading to impairment of oxidative pathways and of energymetabolism. In addition, the excess of free fatty acids can be stored astriglycerides in adipose tissues as well as in lean tissues which maypromote organ dysfunction and metabolic diseases such as hepaticsteatosis or cardiovascular diseases.

The inventors have found that hexanoylglycine may be used as a biomarkerin a body fluid for detecting and/or quantifying the likelihood toresist high fat diet induced weight gain. The body fluid may be urine.Using urine as body fluid has the advantage that it can be obtainedregularly, non-invasively and without the support of medical personnel.

This diagnostic method is practiced outside of the human or animal body.Typically, the biomarker detection and/or quantification step is carriedout in a body fluid sample that was previously obtained from the subjectto be tested.

While the present invention is described in view of quantifying thelikelihood to resist high fat diet induced weight gain, it is clear toskilled artesians that the same method can be also used for quantifyingthe likelihood to be susceptible to a high fat diet induced weight gain.Skilled artesians understand that if an increased level of a biomarkeris indicative for an increased likelihood to resist high fat dietinduced weight gain, a decreased level of a biomarker is indicative foran increased likelihood to be susceptible to a high fat diet inducedweight gain, and vice versa.

Hence the present invention also related to the use of hexanoylglycineas a biomarker in urine for detecting and/or quantifying the likelihoodto be susceptible to high fat diet induced weight gain.

The present invention also relates to a method of diagnosing thelikelihood of a subject to resist high fat diet induced weight gain,comprising determining the level of hexanoylglycine in a urine samplepreviously obtained from a subject to be tested, and comparing thesubject's hexanoylglycine level to a predetermined reference value,wherein the predetermined reference value is based on an averagehexanoylglycine level in urine in a control population, and wherein anincreased hexanoylglycine level in the sample compared to thepredetermined reference value indicates an increased likelihood toresist high fat diet induced weight gain.

The present invention also relates to a method of diagnosing thelikelihood of a subject to be susceptible to high fat diet inducedweight gain, comprising determining the level of hexanoylglycine in aurine sample previously obtained from a subject to be tested, andcomparing the subject's hexanoylglycine level to a predeterminedreference value, wherein the predetermined reference value is based onan average hexanoylglycine level in urine in a control population, andwherein a decreased hexanoylglycine level in the sample compared to thepredetermined reference value indicates an increased likelihood to besusceptible to high fat diet induced weight gain.

Using urine as sample has the advantage that in can be obtainednon-invasively using a well established procedure. The actual diagnosismethod is then carried out outside the body.

The level of hexanoylglycine in the sample can be detected andquantified by any means known in the art. For example, ¹H-NMR, massspectroscopy, e.g, UPLC-ESI-MS/MS, may be used. Other methods, such asother spectroscopic methods, chromatographic methods, labelingtechniques, or quantitative chemical methods may be used as well.Ideally, the hexanoylglycine level in the sample and the reference valueare determined by the same method.

The predetermined reference value may be based on an averagehexanoylglycine level in the tested body fluid in a control population.The control population can be a group of at least 3, preferably at least10, more preferred at least 50 people with a similar genetic background,age and average health status.

The present invention allows it, for example, to stratify subjectsearly, before they put on weight which may result in health risks. Bybeing aware whether one is susceptible to high fat diet induced weightgain, one can adjust lifestyle and diet accordingly early. Anappropriate lifestyle, ideally accompanied by a personalized nutritionalregime allows it to maintain a healthy physique and avoids that one hasto make significant efforts in terms of caloric restrictions and/orexercise regimens to regain that healthy physique.

While hexanoylglycine as sole marker is effective as a tool for thediagnosis method of the present invention, the quality and/or thepredictive power of said diagnosis will be improved, if the diagnosisrelies on more than just one marker.

Hence one or more other markers for diagnosing an increased likelihoodto resist high fat diet induced weight gain and/or for diagnosing anincreased likelihood to be susceptible to high fat diet induced weightgain may be used in combination with hexanoylglycine.

The inventors were surprised to see that also other biomarkers can beused to detect an increased likelihood to resist high fat diet inducedweight gain and/or for diagnosing an increased likelihood to besusceptible to high fat diet induced weight gain.

As such the inventors have identified that increased urineconcentrations of isovalerylglycine, leucine, isobutyrate, acetate, anddecreased urine concentration of trimethylamine-N-oxide, guanidoacetate,sucrose, tartaric acid, hippuric acid and hydroxyphenylacetylglycineallow diagnosing an increased likelihood to resist high fat diet inducedweight gain.

The methods of the present invention may, hence, further comprise thesteps of determining the level of at least one further biomarkerselected from the group consisting of trimethylamine-N-oxide,isovalerylglycine, leucine, isobutyrate, acetate, guanidoacetate,sucrose, tartaric acid, hippuric acid and hydroxyphenylacetylglycine inthe urine sample, and comparing the subject's level of the at least onefurther biomarker to a predetermined reference value, wherein thepredetermined reference value is based on average levels of that atleast one further biomarker in a urine sample of a normal healthycontrol population, and wherein a decreased trimethylamine-N-oxide,guanidoacetate, sucrose, tartaric acid, hippuric acid and/orhydroxyphenylacetylglycine and an increased isovalerylglycine, leucine,isobutyrate, acetate, level in the urine sample compared to thepredetermined reference values indicates an increased likelihood toresist high fat diet induced weight gain. Accordingly, a decreasedisovalerylglycine, leucine, isobutyrate, acetate, and an increasedrimethylamine-N-oxide, guanidoacetate, sucrose, tartaric acid, hippuricacid and/or hydroxyphenylacetylglycine level in the urine samplecompared to the predetermined reference values indicates an increasedlikelihood to be susceptible to high fat diet induced weight gain.

Also the further biomarkers may be detected and quantified by ¹H-NMR ormass spectroscopy, e.g, UPLC-ESI-MS/MS. Other methods, such as otherspectroscopic methods, chromatographic methods, labeling techniques, orquantitative chemical methods may be used as well.

Ideally, all assessed biomarkers are assessed by the same technology.They may be assessed simultaneously.

The method of the present invention may comprise the assessment of atleast 2, at least 3, at least 4, at least 5, at least 6, or at least 7biomarkers.

For example, hexanoylglycine may be assessed together withtrimethylamine-N-oxide.

Hexanoylglycine may also be assessed together with isovalerylglycine.

Hexanoylglycine may also be assessed together with leucine.

Hexanoylglycine may also be assessed together with acetate.

Hexanoylglycine may also be assessed together withtrimethylamine-N-oxide and isovalerylglycine.

Hexanoylglycine may also be assessed together withtrimethylamine-N-oxide, isovalerylglycine, and leucine.

Hexanoylglycine may also be assessed together withtrimethylamine-N-oxide, isovalerylglycine, and acetate.

Hexanoylglycine may also be assessed together withtrimethylamine-N-oxide, isovalerylglycine, acetate, and leucine.

Hexanoylglycine may also be assessed together withtrimethylamine-N-oxide, isovalerylglycine, acetate, leucine, andguanidoacetate.

Hexanoylglycine may also be assessed together withtrimethylamine-N-oxide, isovalerylglycine, acetate, leucine,guanidoacetate and hippuric acid.

The advantage of assessing more than one biomarker is that the morebiomarkers are evaluated the more reliable the diagnosis will become.If, e.g., more than 1, 2, 3, 4, 5, 6, or 7 biomarkers exhibit theelevations or decreases in concentration as described above, thepredictive power for detecting and/or quantifying the likelihood toresist and/or be susceptible to high fat diet induced weight gain isstronger.

The reference value for hexanoylglycine and optionally for the otherbiomarkers is preferably measured using the same units used tocharacterize the level of hexanoylglycine and optionally the otherbiomarkers obtained from the test subject. Thus, if the level of thehexanoylglycine and optionally the other biomarkers is an absolute valuesuch as the units of hexanoylglycine in μmol/l (μM) the reference valueis also based upon the units of hexanoylglycine in μmol/l (μM) inindividuals in the general population or a selected control populationof subjects.

Moreover, the reference value can be a single cut-off value, such as amedian or mean. Reference values of hexanoylglycine and optionally theother biomarkers in obtained body fluid samples, such as mean levels,median levels, or “cut-off” levels, may be established by assaying alarge sample of individuals in the general population or the selectedpopulation and using a statistical model such as the predictive valuemethod for selecting a positivity criterion or receiver operatorcharacteristic curve that defines optimum specificity (highest truenegative rate) and sensitivity (highest true positive rate) as describedin Knapp, R. G., and Miller, M. C. (1992). Clinical Epidemiology andBiostatistics. William and Wilkins, Harual Publishing Co. Malvern, Pa.,which is incorporated herein by reference.

Skilled artesians will know how to assign correct reference values asthey will vary with gender, race, genetic heritage, health status orage, for example.

In the method of the present invention, a decreased likelihood to resisthigh fat diet induced weight gain is indicative for the likelihood todevelop disorders associated with overweight and/or obesity.

“Overweight” is defined for an adult human as having a BMI between 25and 30. “Body mass index” or “BMI” means the ratio of weight in kgdivided by the height in meters, squared. “Obesity” is a condition inwhich the natural energy reserve, stored in the fatty tissue of animals,in particular humans and other mammals, is increased to a point where itis associated with certain health conditions or increased mortality.“Obese” is defined for an adult human as having a BMI greater than 30.

Disorders associated with overweight and/or obesity may be cardiometabolic diseases and/or metabolic deregulations.

The method of the present invention allows it for example to determinethe degree of susceptibility of subjects to diet induced weight gain.The method may hence allow stratifying patients according to theirlikelihood to put on weight based on a high caloric—in particular highfat—diet, independently from whether they are presently underweight,normal, overweight or obese. Adult people are considered underweight ifthey have a BMI equal to or less than 18.5.

The method of the present invention may also be carried out inunderweight, normal, overweight or in obese subjects. In particular inunderweight, overweight or in obese subjects the method of the presentinvention may help to elucidate the genetic predisposition of thesubject. Based thereon—and ideally under further consideration of theirgeneral health status and lifestyle—personalized nutritional regimensmay be developed, that can help to maintain or regain a healthy status.

The method of the present invention is not limited to humans. It mayalso be used in animals, such as companion animals, for example.Companion animals, such as cats or dogs may be analyzed. Based thereonnutritional regimens may be designed that will contribute to a long lifeof the companion animal in good health.

The study presented in this application provides insight in thephysiological mechanisms related to HF (high fat) induced obesitydevelopment and particularly highlights the specific metabolicadaptations associated to obese phenotype variability. High fatingestion provokes a rapid and consistent up-regulation of mitochondrialmetabolic pathways resulting in more production of energy and increasedmitochondrial fatty acid saturation. Among the HF fed mice,obesity-resistant (NR) mice were identified, which particularlyactivated specific mitochondrial metabolic pathways (β oxidation,butanoate metabolism and leucine catabolism) and seemed to maintainenergy homeostasis (activity of Krebs's cycle comparable to LFD). Theinventor's results hence suggest that a specific activation ofmitochondrial oxidative pathways might enable to conserve energyhomeostasis and protect mitochondria against fuel overloading.Therefore, the role of mitochondria seems to be crucial in thedevelopment of obesity and its associated metabolic disorders.Consequently, this comprehensive analysis of the mechanisms underlyingheterogeneous adaptation to HFD feeding provides novel and promisingperspectives for weight management programs and personalized nutritionalsolutions.

Hence, if the method of the present invention allows identifying adecreased likelihood to resist high fat diet induced weight gain—or anincreased likelihood to be susceptible to high fat diet induced weightgain—this may be indicative for a lack of specific activation ofmitochondrial oxidative pathways.

Conversely, if the method of the present invention allows identifying anincreased likelihood to resist high fat diet induced weight gain—or adecreased likelihood to be susceptible to high fat diet induced weightgain—this may be indicative for a specific activation of mitochondrialoxidative pathways.

The mitochondrial oxidative pathways may be selected from the groupconsisting of β oxidation, butanoate metabolism and leucine catabolism.

As the method of the present invention allows the stratification ofsubject without the need to have the symptoms of predispositionsvisible, it is for example suitable for children, teenagers, youngadults and/or a subjects at risk of developing overweight or obesity.

Through awareness, such a risk can be suitably met in terms of diet andlifestyle and the possible risks that may be derived from overweight orobesity later in life can be eliminated.

Hence, the method may be used to devise a stratified diet for a specificgroup of subjects or a personalized diet for a specific subject.

Those skilled in the art will understand that they can freely combineall features of the present invention disclosed herein. In particular,features described for the use of the present invention may be combinedwith the method of the present invention and vice versa. Further,features described for different embodiments of the present inventionmay be combined.

Although the invention has been described by way of example, it shouldbe appreciated that variations and modifications may be made withoutdeparting from the scope of the invention as defined in the claims.

Furthermore, where known equivalents exist to specific features, suchequivalents are incorporated as if specifically referred in thisspecification. Further advantages and features of the present inventionare apparent from the figures and non-limiting examples.

EXAMPLES Animal Handling Procedure and Sample Preparation

The experiment was carried out under appropriate national guidelines atthe Nestlé Research Center (NRC, Switzerland). The mice were maintainedin individual cage under 12 h-12 h of light-dark regime and fed adlibitum during the overall experiment. A total of 80 C57BL/6 micefirstly received a standard CHD (Baseline 3437) for several weeks and afirst collection of urine was carried out following this treatment (t0).Mice were then split in 2 groups: 24 mice were fed with a different CHD(Low Fat D12450B, composition see supplementary figures) in which therate of protein, vitamins, minerals and carbohydrates was different fromthe first standard diet. 56 other mice were fed with HFD (High FatD12492) in which the dietary composition apart from the level ofcarbohydrate and fat, were comparable to the second CHD. These twogroups were respectively characterized as control groups and DIO groups.Once again, urine samples were collected 7 days (t1) and 60 days (t2)after the diet switch. All the samples were snap-frozen at −80 C. untilanalysis. All mice were also weight at t0, t1, t2 in order to monitorthe weight gain in both HFD and control groups. Difference in weightgain of HFD and LFD as well as NR and SR was assessed by non parametrictest (Wilcoxon-Mann-Whitney U test). Food intake (FI) of each mouse wasalso recorded at t1 and t2. There is a significant decrease of FI in HFDfed mice compared to LFD fed mice overtime. SR mice also have higher FIthan NR mice at both time points. The difference of FI between groupswas calculated by Wilcoxon-Mann-Whitney U test.

¹H NMR Spectroscopy

A volume of 40 μl of urine were diluted in 20 μl of buffer solution(NaHPO₄, 0.6M pH=7) containing sodium azide (3 mM) and TSP (0.5 mM).After centrifugation, samples were transferred in 1.7 mm diameter NMRtubes by using a syringe. ¹H NMR spectra were then recorded on 600.13MHz spectrometer, by performing 64 scans of a standard sequence with 64Kdata-points. The temperature of NMR experiment was maintained at 300 K.Processing of urine spectra was carried out by using the softwareTOPSPIN 2.0 (Bruker Biospin, Rheinstetten, Germany). For each spectrum,the FIDs were multiplied by an exponential function corresponding to aline broadering of 1 Hz, prior to being transformed into spectrum by aFourrier Transformer. The phase and baseline of the spectra were thenmanually corrected. The chemical shift was calibrated by using the TSPsignal at δ 0. Spectral assignments were achieved by using STOCSY(Statistical TOtal Correlation SpectroscopY), spectral databases andpublished assignment

Data Processing and Multivariate Data Analysis:

The spectral data (from δ 0.2 to δ 9.5) were finally imported intoMatlab software (version, the mathworks Inc, Natwick Mass.) and weretransformed into 22K data-points. Resonance of water peak (δ 4.7-5.05)was removed from each spectrum in order to eliminate the variabilitylinked to the water resonance presaturation. ¹H NMR spectra were thennormalized on total area and different multivariate statistics (PCA,OPLS, and OPLS-DA) were applied by using “unit variance” scaling. TheOPLS regression coefficient can be displayed using a back-scalingmethod. In this way, we can estimate the proportion of variance of eachNMR variable responsible for group discrimination in the model. Theconstruction of heatmaps showing metabolites with highest coefficientvalues provides an easy comparison of short term and long term metabolicresponses to HFD feeding. Heatmaps were generated by taking the valuesof the correlation coefficient of metabolites discriminating HFD/LFD orSR/NR. Correlation coefficients above the cutoff of 0.3 are displayed bya color map (gradients from red to blue according to the value ofcovariance in each metabolite) Hence heatmaps provide an easy comparisonof the short term and long term metabolic responses to obesitydevelopment.

Univariate Data Analysis

Intermediates metabolites from β oxidation, BCAA oxidation, Krebs'scycle and Nicotinamide adenine dinucleotide pathways assignable on urine1H NMR spectra were integrated in order to assess the urinary excretionof these metabolites 7 days and 60 days after diet switch in LFD, HFD,NR and SR groups. For each metabolite, the integral at 7 days and 60days was divided by the integral at day 0 (during the pre interventionperiod) in order to normalise the urinary excretion of these metabolitesaccording to the baseline. The ratio obtained for each metabolite wascompared between LFD, HFD, NR and SR groups at each timepoint using nonparametric Mann and Whitney test.

Major Findings and Highlights:

Weight Gain Variability in C57BL/6J Mice Fed a HFD.

In order to study the contribution of diets to the development ofobesity, 60 C57BL/6J mice were fed with a chow diet (CHD) during apre-intervention period of 1 week, followed by a diet switch where micewere fed with a LFD (n=20) or a HFD (n=40) for 60 days. Body weight wasmeasured during the pre-intervention period and 7 and 60 days after thediet switch (FIG. 1.A). Weight monitoring showed a significant increaseof weight in HFD fed mice compared to LFD fed mice through theexperiment. In particular, the average weight of HFD fed mice was 1.5 ghigher (p=3.9×10⁻⁷) at 7 days and 4.5 g higher (p=2.36×10⁻⁸) at 60 daysthan control mice. The weight distribution also revealed a strongheterogeneity among the HFD group at 7 days (coefficient of variationCV=0.05), which was even more noticeable at 60 days (CV=0.120) (FIG.1.B). This observation highlights the existence of a strong phenotypicvariability within the HFD group and suggests the existence of specificmetabolic signatures associated to these obese-sub phenotypes.

In order to characterize the “Strong-Responder” (SR) and “Non-Responder”(NR) to HF feeding, we stratified the mouse population according to bodyweight gain (BWG) after 7 days and 60 days of HF feeding. Mice beingconsistently at the top and the bottom thirds of the BWG distributionwere designated as NR and SR mice respectively with the exception of 3SR mice being in the top half of BWG distribution at 60 days. Thisthreshold was selected in order to obtain enough samples in each group(NR mice n=10 SR mice=14) and perform powerful statistical tests as wellas to identify significant difference in metabolic signatures betweenthese two groups. The average weight trajectory of NR, SR and LF fedmice over time (FIG. 1.D) revealed that SR mice gained significantlymore weight than NR mice and LF fed mice during the experiment.Interestingly, there was no significant difference in body weightbetween the NR group and the LFD group at 7 days (p=0.10), but weidentified a significant variation in body weight at 60 days(p=7.67×10⁻⁵). In addition, the body weight gain trajectory of NR mice(regression coefficient=3.85) was similar with LF fed mice highlightingthat the weight gain behaviour of NR mice was comparable to LF miceovertime, whereas SR mice tend to accumulate weight faster. This earlyand sustained inflexion of body weight gain trajectory, defining strongresponder and non-responder subgroups suggests the existence of adifferential predisposition to diet induced obesity (DIO) in C57BL/6Jmice. Hence, we will test in this study the ability to predict weightgain trajectories in HFD-fed mice based on early metabolic profiles.

Urine Metabolic Profiling Points Out Sustained Metabolic SignatureAssociated to High Fat Induced Obesity

To investigate the specific metabolic signature associated withdiet-induced obesity development, we acquired urine metabolic profiles 1week before, 7 and 60 days after the dietary intervention using ¹H NMRspectroscopy (FIGS. 2.A, 2.B). Urine metabolic profiles from LF and HFfed mice were then compared at each time point by using OPLS-DA models.Each model was calculated by using one predictive and several orthogonalcomponents. The optimal number of orthogonal components was determinedby R²Y and Q²Y goodness-of-fit statistics. The OPLS-DA score plots formodels at 7 days (FIG. 2.C) and 60 days (FIG. 2.D) showed that thestrong metabolic variation associated with to HF feeding was highlightedalong the predictive component (Tpred) whilst the second axisillustrating the first orthogonal component (Torth) reflects withingroup variability linked to diet-independent effects.

For each model, the metabolites with the highest correlation coefficientwere identified and summarised in a heatmap (FIG. 2.E) indicating theurinary metabolic variations between LF and HF mice. Specifically, thelevel of carnitine, hexanoylglycine, and the intermediates of BCAAsoxidation (isovalerylglycine, α-keto-βmethylvalerate and α-ketovalerate)were significantly increased in the HF group at 7 days and 60 days.Conversely, the levels of methylamine derivatives produced frommicrobial choline metabolism (trimethylamine (TMA), andtrimethylamine-N-oxide (TMAO)) as well as the end-product ofphenylalanine degradation by gut bacteria (phenylacetylglycine) weredecreased in the HF group during the whole experiment. In particular,the degree of variation in the urinary level of TMAO between 7 days and60 days suggests a time-dependent shift in the conversion of TMA to TMAOunder HFD feeding. Hence, HFD treatment may imply significant changes ingut microbiota activity. Time dependent metabolic adaptation to HFDfeeding was also characterized by a significant reduction ofindoxylsulfate in urine of mice fed a HF for 7 days. End products ofNicotinamide adenine dinucleotide (Nicotinamide adenine dinucleotide)pathways (N1-methyl-2-pyridone-5-carboxamide:2PY andN1-methyl-4-pyridone-3-carboxamide: 4PY) were also positively correlatedwith mice fed a HF for 60 days. The excretion of isovalerylglycine,α-keto-β-methylvalerate and α-ketoisovalerate significantly andconsistently increased in HFD fed group compared to LFD fed groupovertime, so they constitute qualitative and stable candidate biomarkersof DIO.

Urine Metabolic Profiling of NR and SR Mice Highlights a SpecificMetabolic Adaptation Associated to Obesity Prone and Obesity ResistantPhenotype

The establishment of metabolic profiles of SR and NR mice enabled toidentify metabolites associated with the highest divergence in weightgain. Comparisons of ¹H NMR spectral data between NR and SR wereperformed using pair wise OPLS-DA models at 7 days and 60 days (FIGS.3.A, 3.B). OPLS-DA score plot at 7 days (FIG. 3.C), and 60 days (FIG.3.D) displayed a good discrimination between NR and SR mice along thepredictive component (Tpred). The second axis illustrates orthogonalvariation to strong obesity-associated-response. Interestingly, nodifference in urinary metabolic profiles of NR and SR mice wereidentified before the diet switch, which highlights that C57BL/6J miceall have similar phenotypes and metabotypes when they were fed a chowdiet.

The heatmap (FIG. 3.E) summarizing metabolites involved in the groupseparation displayed differential metabolic profiles associated with NRand SR mice during a short-term period (7 days) and a long-term period(60 days) of HF feeding. In particular, a specific metabolic signatureinvolving leucine catabolism, β oxidation, and short chain fatty acidproductions, were associated with the gradation of obesity. Indeed,hexanoylglycine, isovalerylglycine, leucine, acetate and isobutyratewere negatively correlated with SR mice during the overall experiment.As these metabolites are consistently down-regulated in SR mice, theyconstituted the stable candidate marker of obesity-resistant phenotype.The comparison of metabolic profiles between SR and NR mice at 7 daysand 60 days also showed a time dependant metabolic signature associatedwith phenotype variability. A lower urinary excretion of acetate wasobserved in SR mice after 7 days of HFD. By contrast, a higher urinaryexcretion of sucrose was noticed in SR mice at the same period.Surprisingly, taurine was positively correlated with SR mice 7 daysafter of HF feeding and negatively correlated with SR mice after 60days. The urine metabolic profile of SR mice after 60 days of HFD wasalso marked by an increase of creatine, guanidoacetate, tartrate,hippurate, and hydroxyphenylacetylglycine. Interestingly,hexanoylglycine and isovalerylglycine, which were characterised asqualitative candidate markers of DIO, were also identified as stablecandidate marker of obesity-resistant phenotype. These results pointedout that leucine catabolism and β oxidation taking place in themitochondria are strongly affected with HF feeding and their specificregulation might contribute in the onset of obesity.

Urinary Exertion Patterns of Several Metabolites Pointed Out SpecificDeregulations of Mitochondrial Metabolism in HF Mice and SR Mice.

The regulation of mitochondrial metabolism in HFD fed mice was furtherinvestigated with the help of a complementary univariate data analysisapproach (cf method). Urinary excretion of β oxidation intermediates:hexanoylglcyine, carnitine and acylcarnitine were consistently increasedin urine of HF fed mice compared to LF fed mice which suggests anincrease of fatty acid overflow in the mictochondria and an activationof β oxidation. The end product of Nicotinamide adenine dinucleotidepathways (2PY, 4PY) also constantly increased in mouse urine after HFDfeeding which indicates an up-regulation of β oxidation and peroxidomeproliferators. The integrations confirmed that leucine, valine,isoleucine as well as intermediates of BCAAs catabolism(isovalerylglycine, α-keto-βmethylvalerate and α-ketovalerate) weresignificantly and consistently increased in HF fed mice supporting thehypothesis of HFD associated up-regulation of BCAAs catabolism. Krebs'scycle was also partly regulated in HF fed mice as we observed a shortterm urinary increase of succinate in mouse 7 days after HFD, urine ofHF fed mice compared to LF fed mice. These results support thehypothesis that valine and isleucine catabolism is up-regulated inducingthe formation of succinyl-CoA and the production of the followingKrebs's cycle intermediates. Surprisingly, the other Krebs's cycleintermediates (citrate, cis-aconitase, α-ketoglutarate) were notsignificantly different between LF and HF fed mice suggesting adisconnection between leucine catabolism and β oxidation producingacetyl-CoA, and Krebs's cycle. Specific metabolic regulations coulddivert the flux of acetyl-CoA toward other metabolic pathways. Inparticular, the increased level of vinylaceylglycine in urine of HF fedmice suggests that acetyl-Coa could be redirected toward acetoacetyl-CoAwhich is linked to butanoate metabolism and the formation ofvinylacetylglycine. These results confirm that HFD induce anup-regulation of mitochondrial oxidative pathways and Krebs's cyclewhich might lead to an increase of energy production.

Univariate data analysis also enabled us to better understand the linkbetween β oxidation, BCAA catabolism and Krebs's cycle in the context ofphenotype variability. Integrations of BCAA catabolism intermediatesshowed that only isovalerylglycine was significantly higher in urine ofNR mice compared to SR mice or LF mice indicating that obesity-resistantmice were associated with disruption of leucine catabolism exclusively.Hexanoylglycine was significantly higher in urine of NR mice compared toSR mice during the overall experiment whereas the urinary excretion ofcarnitine and acylcarnitine stayed unchanged. Hence, even though βoxidation seemed to be affected in NR mice, fatty acid flow toward themitochondria is consistent between NR and SR mice. In addition, weobserved a significant increase of vinylacetylglycine in urine of NRmice suggesting a redirection of acetyl-coA toward the butanoatemetabolism. Interestingly, no difference in Krebs's cycle activitybetween NR and SR mice were observed after 7 days of HFD. At 60 days,succinate, and were significantly higher in urine of SR micehighlighting a up-regulation of Krebs's cycle. As previously observed,the urinary excretion of other Krebs's cycle intermediates (citrate,α-ketoglutarate, cis-aconitate) were unchanged between NR and SR micesupporting the hypothesis of specific regulation within the Krebs'scycle. Our results indicate that after a long term period of HFD,obesity prone mice are associated with an impairment of energymetabolism which is characterised by a deregulation of Krebs's cycle.The rapid activation of β oxidation, leucine catabolism and butanoatemetabolism in obesity resistant mice may be a protective mechanismagainst fatty acid overflow which enable to maintain energy homeostasis.

Relationships of the highlighted metabolites with weight gain wasassessed using metabolite urinary concentration (as measured by ¹H NMRspectroscopy), fold of change from baseline (TO), and ratio with urinarycreatine (as measured by ¹H NMR spectroscopy). Emphasis was given on thecapacity to predict weight gain and stratify individuals as NR or SR,based on the short term metabolic response to the dietary challenge(namely at T7). The correlation coefficients values are summarized inTable 1, whilst the fold of changes are reported in table 2. To selectthe more robust markers, there was used the % Mean decrease accuracy of‘out-of-bag’ data as variable importance feature. In this way, it waspossible to determine the variables that better discriminate subjectsaccording to their weight gain susceptibility (NR and SR phenotypes,FIG. 5), indicating hexanoylgycine, siovaleroylglycine, TMAO and acetateas the most robust metabolic markers for stratifying subjects as NR orSR phenotypes.

TABLE 1 Summary of relationships between metabolites and weight gain inhigh fat induced weight gain Correlation Coefficient with final WeightCorrelation Coefficient with Final Weight Gain in high fat fed animals(r value) in high fat fed animals (r value) Fold of Ratio Fold of Ratiochange Concentration metabolite/ change Concentration metabolite/Metabolites T7/T0 T7 creatinine T7 (T7/T0) T7 creatinine T7Hecanoylglycine −0.51 −0.38 −0.44 −0.50 −0.32 −0.44 Isovalerylglycine−0.60 −0.42 −0.48 −0.62 −0.36 −0.51 Leucine −0.52 −0.17 −0.16 −0.56−0.03 −0.18 Creatinine −0.08 −0.04 NA −0.09 0.09 NA TMAO 0.27 0.25 0.210.27 0.23 0.17 Hippuric acid −0.09 0.01 0.01 −0.17 0.04 −0.05 Acetate−0.41 −0.48 −0.46 −0.42 −0.41 −0.48 Guanidoacetic 0.13 0.26 0.11 0.100.17 −0.03 acid

TABLE 2 Summary of the fold of changes in selected metabolites over timein weight gain resistant (NR) and prone (SR) individuals T0 T7 T60 NR SRNR SR NR SR Body Weight 102.9 ± 1.4  111.4 ± 2.3  120.6 ± 3.1  149.8 ±11.6 Hexanoylglycine 100 ± 0 100 ± 0 218.5 ± 40.3 177.6 ± 56.8 210.7 ±61.7 160.2 ± 36.4 Isovalerylglycine 100 ± 0 100 ± 0 137.7 ± 21.8 112.6 ±24.4   132 ± 29.3 106.3 ± 17.1 Leucine 100 ± 0 100 ± 0 190.6 ± 17.1177.2 ± 19.6 162.3 ± 23.2 152.9 ± 22.4 Creatinine 100 ± 0 100 ± 0 164.5± 41.6 135.1 ± 41.3 181.3 ± 33.7 165.4 ± 58.7 TMAO 100 ± 0 100 ± 0  63.8± 36.7   80 ± 33.3 101.4 ± 56.7  80.3 ± 57.8 Hippuric acid 100 ± 0 100 ±0 11.9 ± 2.7 12.6 ± 4.7   11 ± 2.4 14.5 ± 4.4 Acetate 100 ± 0 100 ± 0 85.6 ± 28.2  72.9 ± 29.3 115.8 ± 149   75.2 ± 29.3 Guanidoacetic acid100 ± 0 100 ± 0   143 ± 15.1 142.9 ± 19.4 148.2 ± 23.3 152.4 ± 23.7

The invention claimed is:
 1. A method of diagnosing the likelihood of asubject to resist high fat diet induced weight gain, the methodcomprising: determining the level of hexanoylglycine in a urine samplepreviously obtained from a subject to be tested, and comparing thesubject's hexanoylglycine level to a predetermined reference value,wherein the predetermined reference value is based on an averagehexanoylglycine level in urine in a control population, and wherein anincreased hexanoylglycine level in the sample compared to thepredetermined reference value indicates an increased likelihood toresist high fat diet induced weight gain.
 2. The method of claim 1,further comprising the steps of determining the level of at least onefurther biomarker selected from the group consisting oftrimethylamine-N-oxide, isovalerylglycine, leucine, isobutyrate,acetate, guanidoacetate, sucrose, tartaric acid, hippuric acid andhydroxyphenylacetylglycine in the urine sample, and comparing thesubject's level of the at least one further biomarker to a predeterminedreference value, wherein the predetermined reference value is based onaverage levels of that at least one further biomarker in a urine sampleof a normal healthy control population, and wherein an increasedisovalerylglycine, leucine, acetate, and/or a decreasedtrimethylamine-N-oxide, guanidoacetate, sucrose, tartaric acid, hippuricacid and/or hydroxyphenylacetylglycine level in the urine samplecompared to the predetermined reference values indicates an increasedlikelihood to resist high fat diet induced weight gain.
 3. The method ofclaim 1, wherein the levels of the biomarkers are determined by ¹H-NMRand/or mass spectrometry in the sample and in the reference.
 4. Themethod of claim 1, wherein a decreased likelihood to resist high fatdiet induced weight gain is indicative for the likelihood to developdisorders associated with overweight and/or obesity.
 5. The method ofclaim 4, wherein the disorders associated with overweight and/or obesityare cardio metabolic diseases and/or metabolic deregulations.
 6. Themethod of claim 1, wherein the subject is underweight, normal,overweight, or obese.
 7. The method of claim 1, wherein the subject is ahuman or a companion animal.
 8. The method of claim 1, wherein adecreased likelihood to resist high fat diet induced weight gain isindicative for a lack of specific activation of mitochondrial oxidativepathways.
 9. The method of claim 1, wherein an increased likelihood toresist high fat diet induced weight gain is indicative for a specificactivation of mitochondrial oxidative pathways.
 10. The method of claim8, wherein the mitochondrial oxidative pathways are selected from thegroup consisting of β oxidation, butanoate metabolism and leucinecatabolism.
 11. The method of claim 1, wherein the subject is a child, ateenager, a young adult and/or a person at risk of developing overweightor obesity.
 12. The method of claim 1, wherein the method is used todevise a stratified diet for a specific group of subjects or apersonalized diet for a specific subject.
 13. The method of claim 7,wherein the companion animal is a cat or a dog.